The invention generally relates to cooking food on a grill or griddle, and more particularly relates to controlling the temperature of such apparatus.
It is well known that it is desirable to be able to control the heat supplied to a grill or griddle. Accordingly, a control knob is typically provided to adjust the heat source. For example, whether cooking with gas or electricity, the control knob generally will adjust the heat source output from low to high through intermediate graduations. When the cook wants a higher temperature, the control knob is used to turn up the heat. When the cook wants a lower temperature, the control knob is used to turn down the heat.
Adjusting the heating source temperature presents problems. First, the cook knows what temperature he wants the grill to be. However, it is not enough merely to set the heat source output level to attain that temperature because for a given heat output (in BTUS), the temperature of the grill varies as a function of the food load. Accordingly, the cook has to monitor the temperature rather than just set the heat source output level on the heat source control knob.
Second, with an electric heating element, the heat output level for a given control setting can vary as a function of line voltage. Accordingly, the temperature cannot be set by setting the position of a heat source control knob.
A third problem with controlling heat source output rather than temperature is that if the heat output is anything other than high, the heat source operates at a reduced power level while it is warming up to temperature. Operating at reduced power level of course increases the grill or griddle warm up time.
Problems with manually adjusting the heat source can be overcome by regulating the temperature. The device commonly used in temperature regulation is a thermostat. Typically, a thermostat is constructed by attaching a thermocouple (or bimetallic switch) to a location normally on one end of the grill and connecting a wire from the thermostat to an on/off switch within the control knob. When the temperature of the location of the grill where the thermocouple is located reaches a preset point, a sensor within the control knob shuts off the grill. When the grill cools to a second preset point, the thermocouple signals to the sensor to turn on the heat.
Using a thermocouple for temperature regulation presents problems in grill or griddle cook tops. Often the temperature of the grill or griddle is uneven. One location of the grill or griddle may be hotter than another. If the thermocouple is in the hot location, the grill or griddle will not be set to the right temperature. When food is placed on the grill or griddle, the food will cool the location where it is placed. If the food is placed directly over a thermocouple, the average temperature over the grill could become too hot. If the food is placed on a location not near a thermocouple, the average temperature over the grill may remain too cold.
The problem of using a thermostat for regulating the grill temperature is most apparent during the initial heating cycle. When a grill is heated, the response of a thermocouple mounted at the long end of a grill is slow.